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blown away. If such an occurrence has ever taken place, I 
find by calculation that we have to account for thirty-five cubic 
miles of material which represented the cone, and about 
seventeen cubic miles representing the crater, or ill all fifty- 
two cubic miles of material which have disappeared. If the 
action was paroxysmal, surely some of this material ought to 
be found in blocks and boulders, distributed round the outside 
of the big crater. Although I crossed the outside mountain 
in two paths, I must say that I failed to meet with such 
material, in fact I do not remember seeing even a single 
boulder, all was smooth. 
If in spite of this we still hold on to the idea of paroxysmal 
actions, the only refuge which we have seems to be that the 
whole of this vast quantity of material was suddenly dissipated 
as dust. A conclusion of this sort seems to me improbable ; 
and instead of regarding this crater as the basal wreck of 
some large mountain, I should be inclined to look upon it as 
being now as it ever was, the upper crater of an old volcano, 
inside which in more recent times a cone has grown. Although 
at the commencement of the mountain the action may have 
been cataclysmic in its nature, subsequently, however, I should 
think that it grew up higher, partly by the accumulation of 
ashes, but now perhaps by the boiling over of a highly liquid 
trachytic lava. That this latter action has taken place seems 
to be testified by the roughly stratified appearances which are 
exhibited in the ring walls ; the growth has, in fact, been 
probably something like the growth of Mauna Loa in the 
Sandwich Islands, or a geyser tube in Iceland. I may also 
add, that were we to suppose the upper portion of a mountain 
like that which must have existed if we complete in our 
imagination the truncated remains which bound large craters 
such as Asosan to have been blown away, we are, I think, 
assuming that the later eruptions of these mountains were more 
powerful than the first, whereas, I think, experience teaches us 
that the reverse is generally the case, as the action of a volcano 
continues by the quantity of material it piles upon itself. The 
hydrostatic pressure of its new column of lava, the increase in 
size of the cavity produced by evisceration in which we may 
suppose the actuating steam to be confined, are causes which 
will all help to make succeeding outbursts vigorous. No doubt 
examples might be quoted to show the reverse of what is here 
suggested, but I think that many more examples might be 
collected to show its truth ; and certainly if we could regard 
volcanic energy as a whole through all past times, the enfeeble- 
ment in volcanic energy which has taken place would be fully 
recognized. 
Amongst the large craters which I have mentioned, and 
